The Arizona Senate split along party lines as it approved a Republican proposal to revamp the state commission that handles the contentious political issue of redrawing the state's congressional and legislative districts once each decade.

The measure approved Wednesday would increase the Independent Redistricting Commission to nine members with equal numbers of Republicans, Democrats and independents. The commission currently has two Republicans, two Democrats and one independent.

The Senate's 17-13 vote sent the resolution to the House, where approval of the proposed amendment to the Arizona Constitution would put it on the November ballot.

Senate President Steve Yarbrough, R-Chandler, said his proposal would better represent independents and dilute party efforts to dominate redistricting, the Arizona Capitol Times reported.

Democrats said the proposal was politically motivated and that the commission's most recent maps had survived Republican-led court challenges.

Under the constitutional change approved by voters in 2000, the commission is required to draw equal-population districts and take into account goals that include communities of interest, compactness and whether individual districts could realistically be won by both major parties' candidates.